This invention relates to excavators. More specifically, the invention is an excavator that generates zero horizontal reaction force when excavating a surface region.
Lunar soil/regolith excavation is considered a vital requirement for future space missions to the Moon and other extra-terrestrial bodies such as Mars, asteroids, or even comets. The regolith is necessary for purposes of In-Situ Resource Utilization (ISRU) in order to create needed commodities such as propellants, breathable air, buffer gases, water for plant growth, portable drinking water for life support, manufacturing, and science as well as to pursue civil engineering construction such as landing pads, berms, roads, surface stabilization for dust control and thermal heat sinks, foundations, structures, habitats, and micro-meteorite/radiation shielding. The excavation of regolith is extremely difficult because deeper regolith (i.e., at depths of 30 cm and more) has bulk densities as high as 1.8 grams/cm3. Specifically, the very small regolith grain particles (e.g., 0-100 microns) exhibit strong cohesion due to electrostatic forces, van der Waals forces, and interlocking morphology.
In addition to the problems associated with regolith density, the low weight in space surface environments (e.g., the Moon's gravity is ⅙th that of the Earth) means that the mass of the excavator vehicle is of little or no value in terms of generating a reaction force for the excavator blade and scoop. That is, the excavator's blade and scoop cannot penetrate the regolith using conventional excavation techniques. In comparison, Earth-based excavators can utilize a brute force solution simply by making the excavator heavy to thereby create the desired reaction force. Due to the current high costs of lifting goods into space (i.e., approximately $4,000/kilogram), as well as packaging and launch vehicle shroud volume constraints, regolith excavation machines designed for use on extra-terrestrial bodies must necessarily be both small and lightweight. Accordingly, conventionally-designed excavation machines are not suitable options for in-space applications.